Rewrite the special TagsPopupMenu action.

This was quite a major undertaking. But no, we have a very nice menu with a checkbox on the left, followed by icon and text.
Even the submenus have a checkbox.

All this is done by drawing directly with QStyle, so it needs to be tested.

TODO:
You will notice that the menu frame on the right is not drawn.

Actually there is code that draws it, but I dont know why it is not visible.